The present invention relates to a carboxylic acid-based composition for inhibition of corrosion, as well as the application of said composition to inhibiting corrosion both of ferrous and non-ferrous metals.
It is known that in numerous uses, notably and by way of example which should not be considered as limiting, in refrigeration systems using circulating water employing anti-freeze agents, and, among other things, in automobile cooling circuits, carboxylic and dicarboxylic acids and salts thereof are very widely used as corrosion inhibiting agents. Additionally, these acids are employed as atmospheric corrosion inhibitors and, for this purpose, are applied as a coating on materials needing protection. Carboxylic acid derivatives, soluble in lipids, are also employed for protection of the so-called "greasy" type, for example for protecting mechanical parts of engines.
Thus, among other documents, U.S. Pat. No. 4,561,990 which is included herein by reference, describes the use of dicarboxylic acid for this purpose. Similarly, U.S. Pat. No. 4,851,145 describes the use of alkylbenzoic acid for this purpose, or of one of the salts thereof, U.S. Pat. No. 4,588,513 describes the use of dicarboxylic acids or salts thereof. At present, the most frequently used dicarboxylic acid is the C12 acid, which however is expensive.
U.S. Pat. No. 4,687,634 discloses corrosion inhibiting compositions comprising: (1) a major amount of an oleaginous carrier and a minor amount (2) of a hydrophylic co-solvent soluble in oil and (3) a C.sub.7 organic acid and dicyclohexylamine salt. Protection is also of the "greasy" type.
EP-0 251 480 discloses ternary compositions comprising a triazole derivative which there is currently an attempt to eliminate because of environmental protection rules.
S. H. Tan et al. CASS 90: Corrosion-Air, Sea, Soil [Proc. Conf.] Auckland, NZ, 19-23, November 1990 discloses tests relating to the inhibiting ability of various organic constituents including the family of C.sub.6 to C.sub.10 monocarboxylic acids and C.sub.7 to C12 dicarboxylic acids.
FR-A-2 257 703 discloses compositions comprising acids of the C.sub.5 to C.sub.9 acid family. Nevertheless, these patents do not provide a solution to all the problems involved in the use of anti-corrosion agents. Firstly, considering environmental protection rules which are becoming increasingly strict, anti-corrosion additives need to be biodegradable. When considering anti-corrosion action in hard water, in other words with a high limestone content, it is often necessary to add calcium complexing agents in order to avoid the anti-corrosion additive from precipitating out. Adding the complexing agent makes the composition more complex. Frequently, protection of ferrous and non-ferrous metals involve differing measures, and formulations that contain agents of varying types are then required. Current anti-corrosion formulations are complex compositions which differ as a function of the uses for which they are intended.
Work which lead to the present invention showed, in a quite unexpectedly manner, and in any case surprisingly, that in this corrosion-inhibiting application, certain known carboxylic acids give rise to a distinctly improved and unexpected inhibiting action in applications in which such mixtures are generally employed, allowing the above-mentioned disadvantages to be obviated.